Overview of bridge performance during the 2011 Christchurch earthquake

The M-w 6.3 February 22, 2011 Christchurch earthquake was centred 10 km south east of central Christchurch on the edge of the city at a depth of 5 km. Peak Ground Accelerations ( PGA) in the area of Southeast Christchurch were much higher than the design level in the period range of New Zealand road and highway bridges, with exceptional values of vertical acceleration being registered. However, overall most of the bridges performed well, with only eight bridges out of 300 in the area of Christchurch suffering moderate-to-extensive damage. Damage was mainly confined to the bridges spanning the Avon River in the central/eastern part of the city, nearest to the earthquake epicentre. The majority of damage was a result of lateral spreading of the river banks, with only three bridges damaged on non-liquefiable sites. Extensive disruption to traffic occurred due to the closure of bridges critical to the network.